1. Field of the Invention
The present invention relates to a method of forming an insulating film containing silicon, and to a semiconductor device and, more particularly to a technology valuable for forming the insulating film containing silicon having a low dielectric constant.
2. Description of the Prior Art
In recent years, miniaturization of the semiconductor device such as LSI, etc. progresses and thus wiring distances in the semiconductor device are reduced year by year. If the wiring distances are reduced in this manner, the parasitic capacitances of the wirings are increased and thus the operation speed of the semiconductor device is slowed down. Therefore, there is the possibility that the higher speed of the semiconductor device is prevented.
As one of the solutions to prevent such increase in the parasitic capacitances of the wirings, the insulating film having the low dielectric constant can be employed as the interlayer insulating film. The SiO2 film is widely employed as the interlayer insulating film in the prior art. However, in order to reduce the wiring capacitances, the insulating film having the lower dielectric constant than this SiO2 film must be employed. The relative dielectric constant of the SiO2 film is 4.1, and up to the present there are following films that are known as the insulating film containing silicon having the lower dielectric constant than that of the SiO2 film.
(1) SOG (Spin On Glass) film
(i) HSQ (Hydrogen Silsesquioxane) film Dielectric constant 3.1 to 3.5
(ii) MSQ (Methyl Silsesquioxane) film Dielectric constant 2.8 to 2.9
(2) FSG (Fluorinated Silicon Oxide) film Dielectric constant 3.5
With regard to the dielectric constant of above films, we referred to Table 1 set forth in xe2x80x9cMonthly Semiconductor Worldxe2x80x9d, page 52, October, 1999.
It is an object of the present invention to provide a method of forming a noble insulating film containing silicon that is different from these insulating films in the prior art, and a semiconductor device using such insulating film.
According to the film forming method of the present invention, the insulating film containing silicon (hereinafter simply refer to as insulating film) is formed on the substrate by plasmanizing the compound having the siloxane bonds and the oxidizing gas to react with each other. Here the Si (silicon) atom in the xe2x80x9ccompound having the siloxane bondsxe2x80x9d have already been bonded with O (oxygen) in the form of the siloxane bond (Sixe2x80x94Oxe2x80x94Si). Therefore, in forming the film, it is difficult for C (carbon) to newly bond with the Si atom in the insulating film formed by using this compound. As a result, it is hard to form many Sixe2x80x94C bonds in the insulating film, and thus the number of Sixe2x80x94C bonds in the film is reduced.
It is generally known that the increase in the number of Sixe2x80x94C bonds in the film causes the increase in leakage current of the film. As described above, since the number of Sixe2x80x94C bonds in the film can be reduced in the insulating film formed by the film forming method of the present invention, the increase in the leakage current of the film can be suppressed.
Particularly, when H2O is used as the oxidizing gas, an amount of NH3 in the insulating film can be reduced. Therefore, when the chemical amplification resist coated on the insulating film is patterned, the resist is not crosslinked by NH3 and thus the resist can be patterned finely. As a result, if the chemical amplification resist is used as an etching mask, it is possible to perform desirably the fine patterning of the insulating film underlying the resist.
Also, according to another film forming method of the present invention, the insulating film is formed on the substrate in the atmosphere in which the high-frequency power is applied to the upper and lower electrodes of the parallel plate type plasma chemical vapor deposition equipment, and the reaction gas containing (Si(CH3)3)2O and N2O is introduced into the chamber. Here, (Si(CH3)3)2O is an example of the aforementioned xe2x80x9ccompound having the siloxane bondxe2x80x9d, and N2O is an example of the aforementioned oxidizing gas. Therefore, as described above, the increase in the leakage current can be reduced in the insulating film formed by this film forming method.
Also, it becomes apparent that if the high-frequency power is applied to both the upper and lower electrodes like this film forming method, the dynamic hardness of the insulating film can be increased compared to the case where the high-frequency power is applied only to the upper electrode.
In addition, according to the results of the examination made by the inventors of this application, it became apparent that if the pressure of the atmosphere in this case is set to more than 0.5 Torr, the dielectric constant of the insulating film can be reduced smaller than that of the conventional SiO2 film.
Further, according to another film forming method of the present invention, the insulating film is formed on the substrate in the atmosphere in which the distance between the upper and lower electrodes of the parallel plate type plasma chemical vapor deposition equipment is set to more than 25 mm. In this case, the high-frequency power is applied only to the upper electrode and not to the lower electrode, and the reaction gas containing (Si(CH3)3)2O and N2O is introduced into the chamber. As described above, the increase in the leakage current of the insulating film can be reduced. Besides, according to the results of the examination made by the inventors of this application, it became apparent that if the distance between the upper electrode and the lower electrode is set to more than 25 mm in this manner, the dielectric constant of the insulating film could be lowered.
Also, according to still another film forming method of the present invention, the Si(OR)nHm compound may be used in place of the compound having the siloxane bond. Here R denotes an alkyl group, n+m=4, and mxe2x89xa70.
In this Si(OR)nHm compound, the Si atom is not directly bonded with R but bonded with R via O (oxxygen). Hence, if the Si(OR)nHm compound is used, Sixe2x80x94C bonds are difficult to be formed in the insulating film. Therefore, like the compound having the siloxane bonds, it is difficult to form a large number of Sixe2x80x94C bonds in the insulating film by using the Si(OR)nHm compound, and thus the number of Sixe2x80x94C bonds in the film can be reduced. As a result, the increase in the leakage current due to many Sixe2x80x94C bonds can be reduced in this insulating film.
It should be noted that a plasma process may be employed after the formation of the insulating film, which is formed using the compound having the siloxane bonds or the Si(OR)nHm compound, in order to improve the hygroscopicity resistance of the film. In this plasma process, the atmosphere containing at least one of O2, N2O, and NH3 is plasmanized and then the surface of the insulating film is exposed to the plasmanized atmosphere.
According to this, H2O contained in the film and CO2 formed in this plasma process by oxidizing C in the film are discharged to the outside of the film, and also unbonded bonds of Si in the film are terminated by O, N, H, etc. Therefore, unbonded bonds of Si in the insulating film can be prevented from being bonded by OH group and the like, and thus the hygroscopicity resistance of the insulating film can be improved.